1. Field of the Invention
This invention relates to the production of gamma-butyrolactone, and, more particularly, to a process for the recovery of purified BLO in high yield from its crude reactor effluent.
2. Description of the Prior Art
Attig, in EPO 322,140, published Jun. 28, 1989, described a process for the production of THF and BLO in which the reaction products of THF and BLO were separated by fractional distillation; by-products and unreacted feed, were returned to the hydrogenation stage; and acidic by-products were removed by treatment with alkali before distillation.
Franko-Filipasic, in U.S. Pat. No. 3,113,138, described a liquid phase process for making BLO by catalytic hydrogenation of succinic anhydride in an organic solvent; recovering the BLO by filtering to remove catalyst; distilling at atmospheric pressure to remove solvent and water; and distilling the product residue at reduced pressure.
Wada, in U.K. patent application No. 2,194,232, published Mar. 2, 1988, while describing a method for making BLO, stated that "the desired lactone may be recovered from the reaction solution by a usual separation and purification means such as distillation or extraction. Further, the distillation residue may be recycled to the reaction system as a catalyst component".
Dunlop, in U.S. Pat. No. 3,065,243, was directed to the reduction of dicarboxylic acid esters and anhydrides to BLO by catalytic hydrogenation in the vapor phase; the process gave a mixed condensate comprising succinic anhydride, BLO and water, which was fractionally distilled to provide BLO in 70-80% conversion.
Broecker, in U.S. Pat. No. 4,048,196, described a multi-stage process for the manufacture of butanediol and/or THF from maleic and/or succinic anhydride via BLO. In the first stage, maleic anhydride, or succinic anhydride, was hydrogenated in the presence of added BLO over a fixed-bed catalyst to give BLO; then the water formed during the hydrogenation was removed by feeding the reaction mixture to the middle section of a distillation column; followed by isolating water and BLO, on one hand, and succinic anhydride and BLO, on the other hand; recycling succinic anhydride and BLO; and finally, separating BLO and water by distillation.
Kouba, in U.S. Pat. No. 4,656,297, described a process for the coproduction of butanediol and THF and their subsequent separation from the reaction product mixture containing water and methanol by a series of distillations including a superatmospheric distillation.
Other references, including DeThomas, U.S. Pat. No. 4,105,674; Mitsubishi, Japan 49-9463; Michalczyk, U.S. Pat. No. 4,006,165; Miya, U.S. Pat. No. 3,580,930; Miller, U.S. Pat. No. 4,001,282; Michalczyk, U.S. Pat. No. 3,948,805; Bridge, U.S. Pat. No. 4,810,807; and Tonen, EPO 373,946; described related processes, without, however, mentioning the separation and/or purification of the desired product from its reaction effluent mixture.
Vapor phase catalytic hydrogenation of maleic anhydride to BLO under high conversion and high selectivity conditions can be carried out by passing a vapor mixture of maleic anhydride feed compound and hydrogen over a suitable catalyst of defined composition. What is desired, however, is to recover the BLO product in purified form and in high yield from the crude reactor effluent which includes in addition to BLO, tetrahydrofuran (THF), water, organic acids and alcohols; and, as has been discovered herein, a small amount of 4-hydroxybutyric acid, which is formed by acid-catalyzed hydrolysis of BLO.
Accordingly, it is an object of this invention to provide a process for the recovery of purified BLO in high yield from its crude reactor effluent.
Another object of the invention is to upgrade the yield of purified BLO from the crude reaction effluent by dehydration and cyclization of the 4-HBA component present in the crude reactor effluent to BLO while separating and removing the water of dehydration to prevent renewed acid hydrolysis of the BLO.
These and other objects and features of the invention will be made apparent from the following description thereof.